Method of separating the constituents of gaseous mixtures



April 7, 1931-. c c, VAN s ET AL 1,799,937

METHOD OF SEPARATING THE'CONSTITUENTS OF GASEOUS MIXTURES Filed Oct. 12,

R mm ww w 4 L M r3064 I ATTORNEY s stituents of a-gasousmixture such as air- Patented Apr. 7, 1931 I UNITED STATES' PATENT OFFICE n. Y., A CORPORATION or NEW Ionx CLAUDE C. VAN Iil'UYS, .0! CBANFOBD, AND JOSEPH I4. SGHLIT'I', OF ELIZABETH, NEW JERSEY, ASSIGNOBS TO AIR REDUCTION COMPANY, INCORPORATE), 0! NEW YORK,

METHOD OF SEPABATING THE CONSTITUENTS OF GABEOUS mrms Application filed October 12,1927. 'Serial Io. 825,848.

This inventlon relates to the separation of the constituents of gaseous mixtures, and particularly to the recovery of oxygen and nitrogen from the atmosphere.

The ordinary method of treating air to separate the constituents oxygen and nitrogen comprises the compression of the air, the cooling and expansion thereof followed by liquefaction, and rectification of the liquid obtained. Thus, in the well known Claude method a liquid containing approximately 47% of oxygen is obtained by selective liquefaction of theentering gaseous air, and this liquid is subjected to rectification with vapors formed at the lower part of the rectification column by evaporating a portion of the liquid produced by rectification. The more complete separation of oxygen from the va.-' pors rising through the column is accomplished by the introduction of a liquid consisting princigally of nitrogen at the top of the column. y modifying the operation of the rectification column it is possible to obtain either substantially pure oxygen or substantially pure'nitrogen, but the operation always involvesa .loss of one or the other of these elements. This is necessary because an the descending liquid or an excess of'nitro gen must be permitted to return with the liquid in order to ensure the complete removalof 0 gen from the nitro en product; It is the dbject' of the present invention to provide a simple and eflicient} method of and apparatus for separating the constituents of gaseous mixtures,-and more particularly to permit the simultaneous recovery of two conin a substantially pure form.

Other objects and advantages of cation and accompanying drawing, in which an apparatus adapted for the practice of the v invention is illustrated diagrammatically. It

should be observed that those details of the apparatus which are well understood by per the in I vention will be apparent as it is better 'understood by reference to the following specificooling, is divided into two parts; one art is hquefied by the outgoing roducts to e utilized as hereinafter descri d; the remainder is further cooled b expansion and is selectively liquefied an rectified. The rectification is so conducted as to separate one of the constituents, for example, nitrogen, in a condition of substantial purity. This can be accomplished readily so that an efiluent consisting, for example, of substantially pure nitrogen can be wit drawn continuously from the apparatus. The complementary liquid which results from the rectification will consist generally of oxygen but will contain substantial proportions of nitrogen and substantially all of the argon present originally in the air. This liquid is withdrawn fromthe primary rectification and together with the liquefied ortion of the original gaseous mixture is su jected to an auxiliary rectification [sure whichexists in the primary rectification and without recompression or recirculation of the efiiuent. It is so conducted that the liquid consists of the second constituent, for example oxygen, in substantial urit The eflluent will be of the com ositlon w 'ch is in phase equilibrium with t e liquefied original gases and will, therefore, re resent a loss of th nitrogen and oxygen. evertheless, it is possible in conducting the operation to obtain substantially the same yolume of oxygen from an apparatus of given size as would be obtained by the single rectification method heretofore employed and at the same time torecover alarge volume of pure nitrogen.

The method as described depends upon the operation as outlined and is a plicable as a modification of various meth ofliquefaction and separation which are now incommercial use. One application in the modifivolves the operation of a Claudecolumnwhich will be designated as the primary column as cation ofthe well known Claude method inindicated auxiliary rechfymg col- 0 umn to se arate the constituents of the liquid obtained by the primary rectification. In such a method air, for example, is compressed to a pressure suflicient to afford the necessary refrlgerative efiect in the system and after cooling by heat exchange with outgoing products the air is separated into two parts, one part being delivered at the initial pressure to a liquefier wherein it is liquefied by heat exchange with the products of the columns. This liquid is delivered to the top of the auxiliary column. The other part of the entering air is expanded in a suitable engine or turbine to a materially lower pressure, and being thereby cooled it enters the bottom of the primary column. The entering air then passes through a plurality of tubes in a vaporizer. the tubes being surrounded by liquid produced in the rectifying compartment of the column and by the liquid produced in the auxiliary column. The gas, such as air, is partially liquefied and the liquid returns and is delivered to an intermediate level of the rectification column and flows downwardly therein in contact with vapors rising from the liquid in the vaporizer. The result is a rectification and consequent separation of nitrogen from the liquid. The uncondensed portion of the entering air in the tubes of the vaporizer is conducted to a condenser at an intermediate level of the rectifier and is there liquefied to produce a reflux consisting substantially of nitrogen. The reflux enters the top of the rectifier and flows downwardly therein in contact with the rising vapors, thereby washing oxygen from the vapors and replacing this element with nitrogen. As the result an efliuent consisting of substantially pure nitrogen is formed and this escapes from the top of the rectifier, the rectification being so operated as to permit a proportion of the nitrogen to descend with the liquid which ac cumulates about the tubes of the vaporizer.

The liquid thus accumulated is partially vaporized by heat exchange with the entering air which is thereby liquefied. The vapor produced is utilized primarily for the purpose of the primary rectification. The surplus vapor is withdrawn and discharged as a waste product. It consists largely of oxygen with certain proportions of nitrogen and argon. That portion which is not evaporated is de livered toan intermediate level of an auxiliary rectifier. The liquefied portionof the original gaseous mixture together with liquid from the primary column descends in contact with vapors formed from the liquid product of the auxiliary rectification. The liquid so formed is delivered to a special compartment of the vaporizer in the primary column and is there vaporized by heat exchange with the gaseous mixture entering the tubes. The vapor consists of substantially pure oxygen and a portion is delivered to the auxiliary rectifier while the balance is withdrawn as one of the products of the operation.

An apparatus ca able of operation in the manner last descri ed is illustrated in the accompanying drawin in which 5 indicates a primary column WhlCll is divided by partitions 6, 7 and 8, into compartments 9, 10, 11 and 12, the latter being the rectifying section of the column. The cooled and expanded air enters the compartment 9 through a pipe 13 and after passing through a plurality of tra s 14 in the compartment it enters a plurallty of tubes 15 which extend through the compartments 10 and 11 to a header 16. In passing through the tubes the air is partially liquefied and returns in contact with the entering gaseous mixture to the trays 14 in the compartment 9. The liquid enriched in oxygen accumulates in the bottom of the compartment 9 and passes through a pipe 20 having a pressure-reducing valve 21 to an intermediate level of the rectifier compartment 12 and descends therein over a plurality of trays 22 of the form usually employed in rectification apparatus. The liquid eventually passes through a tube 23 to a plurality of tra s 24 in the compartment 11 and surrounding the tubes 15.

The unliquefied residue of the air which reaches the header 16 passes through a pipe 25 to a condenser 26 at an intermediate level of the rectifying compartment 12,'and being there cooled by liquids accumulating in the compartment 12 it is 1i uefied and is delivered through a pipe 27 aving a pressurereducing valve 28 to the uppermost level of the rectifying compartment 12 wherein it descends over the trays 22. This liquid is substantially pure nitrogen and acts as a reflux for the vapors rising'in the column. By suitable regulation of the operation these vapors, when they reach the point of introduction of the liquid from the pipe 27, are also substantially pure nitrogen-and this effluent escapes through a pipe 29.

. The liquid accumulating in the bottom of the compartment 11 is partially evaporated to provide the vapor necessary for rectification in the compartment 12, and the remainder is withdrawn through a pipe 30 controlled by a valve 30 and delivered to an intermediate level of an auxiliary rectifier 31 having a plurality of trays 32 therein. The liquid, together with the liquid from the liquefier 17,

escends over the trays in contact withvapor which is introduced through a pipe 33 extending from the com artment 10 of the primary column to the ottom of the auxiliary rectifier 31. A pipe 34 delivers liquid from the bottom of the auxiliary rectifier to the compartment .10 and therein the liquid is vaporized by heat exchange with the entering gaseous mixture to produce the oxygen vapor which is utilized in completing the rectification in the auxiliary rectifier'31. The

surplus va or-iswithdrawn through a ipe 35. The e uent from the auxiliary recti cation escapes through a pipe 36 from the top of the auxiliary rectifier 31 and consists of a mixture of nitrogen, argon and oxygen of the composition in phase equilibrium with liquid air which can be discarded or utilized as desired.

The necessary refrigeration is maintained by heat exchange of the outgoing products with the gaseous mixture entering the system. The liquefier 17 comprises a plurality of tubes 37 and 38 enclosed in a suitable shell. The pipe 29, which de livers the efiluent from the top of the primary rectifier, is connected with a chamber 38 at one end of the liquefier and this chamber communicatesthrough the tubes 38 with a corresponding chamber 39 a t the opposite end of the liquefier. At the latter chamber the gas is delivered through a pipe 40 to a chamber 41 at one end of an exchanger 42. The exchanger comprises pipes 43,43" and 44 enclosed in a suitable shell. The eflluent '2'5 proceeds from the chamber 41 through the pipes 43 to a'corresponding chamber45 at the opposite end-of t e exchanger and is delivered thence through a pipe 46 controlled by a valve 47. The efliuent, substantially- 30 pure nitrogen, for example, can be delivered to a suitable storage receptacle.

The other constituent of the gaseous mixture, for example oxygen, is delivered by a pipe 35 to a chamber 48 at one end of the 3 $6 liquefier 17 and proceeds thence through the tubes 37' to a corres onding chamber 49 at the opposite end of t e liquefier. A pipe 50 delivers the gas to a chamber51 at one end of the exchanger 42 and the gas asses thence through the tubes 43to a cham r 52 at the opposite end of .the exchanger whence it passes througha pipe 53 controlled by a valve to any suitable storage receptacle. The efiluent from the auxiliary rectifier 31 is delivered through the pipe 36 to a chamber 55 atone .end of the liquefier 17, passes through the tubes 38 toa chamber 56 and thence through a' pipe 57 to a chamber 58 at one end of the exchanger 42. Thence it is delivered through the pipe 44 to a correspondingchamber 59 and it escapes .through a pipe 54 controlled by a valve 61.

All of the vapor produced in the compartment 11 not be required for use in rectification in the compartment 12. The surplus vapor'is withdrawn through a pipe 31 in the desired proportion under control of a valve 32 to' efi'ect the desired condition in the compartment 12. The surplus vapor is delivered by the pipe 31' to the chamber 55 of the liquefier 17' and combined with the effluent from the auxiliary rectification.-

The entering gaseous mixture, after being previously compressed in any suitable com pressor, provided with the usual means for in the system absorbing the heat of compression, is delivered through a pipe 62 to the ex'chan r 42 and passes about the baflles 63 therein, eing thus cooled by heat exchange with the products of the separation. The cooled gaseous mixture escapes through a pipe 64 and a portion is diverted through a pipe 65 to the liquefier 17 wherein it passes about the baflles 66. The liquid from the liquefier 17 is delivered through the pipe 19 controlled by valve 18 to the top of the auxiliary column. It acts as a reflux from the auxiliary column and descends over the trays in contact with the rising vapors. The balance of the gaseous mixture is'delivered through pipe 67 and valve 68 to an expansion engine 69 wherein it is expanded and cooled. It is delivered from the expansion engine to they compartment 9 of the primary column bya pi e 13.

' t will be observed that in the operation as described there is but one compression of the entering gaseous mixture and, that conseuentl the power inputcan be reduced to t e minimum. It is possible, nevertheless, with'relatively slight losses to separate a large volume of substantially pure oxygen from the atmosphere and to recover simultaneously in the pure state substantially all the nitrogen in the original mixture delivered to the primary column.

While the invention has been describedwith reference especially to the separation of the constituents of the atmosphere, it should be understood that it is applicable to the separation of constituents of other gaseous mixtures in which the physical properties of the constituents are related in such a way as to permit the separation as in the. case of oxygen and nitrogen of the atmosphere.

tails of operation and in the arrangement of the apparatus employed without. departing from the invention or sacrificing any of the advantages thereof. J

We claim: t 1. The method of separating the constituents of a gaseous mixture, which comprises compressing and cooling the-mixture and liquefying a portion thereof, further cooling mixture having the initial composition o f this mixture as a-reflux liquid inthe auxiliary rectification and brin 'ng the liquid product:

of the auxiliary rectification into heat ex- 105 'Variouschanges may be made in the defication to an-auxiliary recti cation with a change relation with the gases undergoing liquefaction for the primary rectification.

' 2. The method of separating the constitucnts of a compressed gaseous mixture, which comprises selectively liquefying and rectifying one portion of the compressed mixture with a reflux composed of the liquefied gaseous residue of'the selective liquefaction to obtain one constituent as a substantially pure gas and an impure liquid liquefying the other portion of the original mixture, subjecting said impure liquid to an auxiliary rectification. with the liquefied portion of the original mixture having the initial composition of this mixture to obtain another constituent as a substantially pure liquid and returning said liquid to the primary rectification to supply the necessary refrigeration.

3. The method of separating the constituents of gaseous mixtures, whichcomprises rectifying a liquid enriched in one of the constituents and produced by liquefaction of the gaseous mixture with a reflux consisting of another constituent to separate the latter constituent in substantial purity therefrom, sub jecting the liquid resulting from the primary rectification to an auxiliary rectification with a liquefied portion of the original gaseous mixture having the initial composition of this mixture, evaporating the liquid product of the auxiliary rectification solely by heat exchange with the aseous mixture undergoing liquefaction an utilizing a portion of the resulting vapor in the auxiliary rectification.

, 4. The method of separating the constituents of gaseous mixtures, which comprises rectifying a liquid enriched in one of the constituents and produced by liquefaction of the gaseous mixture with a reflux consist ing of another constituent to separate the latter constituent in substantial purity therefrom, subjecting the liquid resulting from the primary rectification to an auxiliary rectification with a liquefied portion of the original gaseous mixture having the initial composition of this mixture, evaporating the liq- -uid product of the auxiliary rectification ith the gaseous solely by heat exchange mixture undergoing lique action, utilizing a portion of the resulting vapor in the auxiliary rectification and passing the efiluent from the auxiliary rectification in heat-exchange relation with said portion of the original gaseous mixture. f

5. The method of separating the constituents of gaseous mixtures, which comprises rectifying the vapors from a liquid enriched in one of the constituents and produced by liquefaction of the gaseous mixture with a liquid consisting substantially of another constituent to separate the latter constituent in substantial purity therefrom,.sub 'ecting the liquid resultingfrom the rimary rectithere rom, subj ectin liquefied portion of the original gaseous mixture having the initial composition of this mixture, evaporating the liquid product of the auxiliary rectification solely by heat exchange with the gaseous 'mixture undergoing liquefaction and utilizing a portion of the resulting vapor in the auxiliary rectification.

6. The method of separating the constituents of gaseous mixtures, which comprises rectifying the vapors from a liquid enriched in one of the constituents and produced by liquefaction of the gaseous mixture with a liquid consisting substantially of another constituent to separate the latter constituent in substantial purity therefrom, subjecting the liquid resulting from the primary rectification to an auxiliary rectification with a liquefied portion of the original gaseous mixture having the initial composition of this mixture, evaporating the liquid product of the auxiliary rectification solely by heat exchange with the gaseous mixture undergoing liquefaction, utilizing a portion of the resulting vapor in the auxiliary rectification and passing the efliuent from the auxiliary rectification in heat-exchange relation with said portion of the original gaseous mixture.

7. The method of separating the constituents of air, which comprises rectifying a liquid enriched in oxygen and produced by I liquefaction of the air with a nitrogen reflux to separate nitrogen in substantial purity therefrom, subjecting the liquid containing oxygen,- argon and nitrogen resulting from the primary rectification to in auxiliary rectification with a liquefied por ion of the original gaseous mixture having the initial composition of this mixture, evaporating the liquid oxygen product of the auxiliary rectification solely by heat exchange with the air undergoing liquefaction and utilizing a portion of the resulting oxygen vapor in the auxiliary rectification.

8. The method of separating the constituents of air, which comprises rectifying. a liquid enriched in oxygen and produced by liquefaction of the air with a nitrogen reflux to se arate nitrogen in substantial purity the liquid containing oxygen, argon and nitrogen resulting from the primary rectification to an auxiliary rectification with a liquefied portion of the original gaseous mixture having the initial comcation solely by heat exchange with the air undergoing liquefaction, utilizing a portion of the resulting oxygen vapor in the auxiliary rectification, and passing the 'efiluent containing nitrogen and argon from the auxiliary rectification vin heat-exchange relation with said portion of the originalgaseous mixture.

9. The method of separating the constituents of a1r, wh1c h comprises rectifying the vapors from a liquid enriched in oxygenand nitrogen reflux to separate produced by liquefaction of the air with a nitrogen reflux to separate nitrogen in substantial purity therefrom, subjecting the liquid containing oxygen, argon and nitrogen resulting from the primary rectification to an auxiliary rectification with a liquefied portion of the original gaseous mixture hav ing the initial composition of this mixture, evaporating the liquid oxygen product of the auxiliary rectification solely vby heat exchange. with the air undergoing liquefaction and utilizing a portion of the resulting oxygen vapor in the auxiliary rectification.

10. The method of separating the constituents of air, which'comprises rectifying the vapors from a-liquid enriched in oxygen and produced by liquefaction of the air with a nitrogen in substantial purity therefrom, subjecting the liquid containing oxygen, argon and nitrogen resulting from t e primary rectification to an auxiliary rectification with a liquefied portion of the original gaseous mixture having the initial composition of this mixture, evaporating the liquid oxygen product of the auxiliary rectification solely by heat exchange with the air undergoing liquefaction, utilizing a portion of the resulting oxygen vapor in the auxiliary rectification, and passin the efliuent containing nitrogen and argon om the auxiliary rectification in heat-exchange relation with said portion of the original aseous mixture.

11. The method of separating the constituents of gaseous mixtures, which comprises conveying the gaseous mixture in heat ex- 7 change relation'successively with a liquid consisting of one of. the constituents in substantial purity and a liquid enriched in that constituent, rectiging the liquid thus produced with a re ux consisting of another constituent to separate the latter constituent in substantial purity, subjecting the liquid resulting from the primary rectification to an auxiliary rectification with a liquefied portion of the original gaseous mixturehaving the initial composition of this mixture, re-

I turning the liquid product of the auxiliary ents of gaseous mixtures,

rectification to replenish the supply of liquid for heat exchangewith the entering gaseous mixture, evaporating this liquid solely by heat exchange .with the entering gaseous mixture and utilizing a portion of the vapor thus.

reduced in the auxiliary rectification. 12. The method of separating the constituwhich comprises the gaseous mixture 'in heat exwith a liquid consisting of one of the constituents in substantial purity and a liquid enrichedin that constitutent, recti 'ng the liquid thus proconveying i duced with a reflux consisting of another constituent to separate the latter constituent in substantial purity,

. mixture.

subjecting the liquid 'resulting from the primary rectification to an aum'liary rectification with a liquefied portion of the original gaseous mixture having the initial composition of this mixture, returning the liquid product of the auxiliary rectification to replenish the supply of liquid for heat exchange mixture, evaporating this liquid so ely by heat exchange with the entering gaseous mixture, utilizing a portion of the vapor thus producedin the auxiliar rectification and passing the efliuent from t e auxiliary rectification in heat-exchange relation with said portion of the original gaseous mixture.

13. The metho of separating the constituents of air, which comprises conveying the air in heat exchange relation successively with a liquid consisting of oxygen-in substantial purity and a liquid enriched in oxygen, rectifying the liquid thus produced with a nitrogen reflux to separate nitrogen in substantial purity therefrom, sub ecting the liquid product of the primary rectification containing oxy en, argon and nitrogen to an auxiliary recti cation with a liquefied portion of the original gaseous mixture having the initial composition of this mixture, returning the liquid oxygen produced by the auxiliary rectification to replenish the supply of'liquid for heat exchange with the air, evaporating the liquid solely by heat exchange with the air and utilizing a portion of the vapor thus produced in the auxiliary rectification.

14. The method of separating the constituents of air, which comprises conveying the air in heat exchange relation successively with a liquid consisting of oxygen in substantial purity and a liquid enriched in oxygen, rectifying the liquid thus produced with .a nitrogen reflux to separate nitrogen in substantial purity therefrom, sub1ecting the liquid product of the primary rectification containing oxy en, argon and nitrogen to an auxiliary rec cation with a'liquefied portion of the original gaseous mixture having the initial composition of this mixture, returning the (End oxygen producedby the auxiliary recti cation toreplenish the supply of liquid for heatfexchange'with the air, evaporating the liquid solely by heat exchange with the air, utilizing a portion of the vapor thus produced in the auxiliary rectification, andipassing the efiluent from the auxiliary rect' cation in heat-exchange relatlon with said portion of the original gaseous Intestimony whereof we aflix our signatures.

UDE C. VAN NUYS,

CLA JOSEPH L. SCHLITT.

with the entering aseous 

